For a canvas-based app, which to be fair none of my professional work has been, you’d need to write some JS or hooks to interface with external JS libraries.
Can you give me an example of when you would need a LiveView app to spawn a thread or set up an observer via JS?
Spawning a thread sounds particularly odd given that JS isn’t running on the server. Are you speaking of web workers? Or do you mean doing something from JS code to send a message to the Phoenix server to get it to spawn a process (i.e., a green thread) on the server?